Watch 5 — Spec (concept stage)

Status: future — open for refinement after Watch 4 ships Concept: The technical stretch — complications New skill this build introduces: Research, planning, problem-solving beyond simple three-hand builds. This build will take ~3× longer than any previous build. That is the point.

Aesthetic

• Form follows function. The complication drives the dial layout.
• Likely 41–42mm to accommodate the more complex movement and the additional dial-side hardware.
• This is a tool watch by definition — there's no minimal-dial version of a chronograph or GMT.

Constraints — early thinking

• Two complication paths to choose between (do not attempt both as a single build):
  • GMT path — Seiko NH34 movement. Adds an independently-set 24-hour hand. Bezel insert is the second timezone. Less mechanical complexity than chronograph; closer in spirit to Watches 1–3.
  • Chronograph path — Valjoux 7750 or similar (Seagull ST19 is a budget option; Sellita SW500 is a premium option). True mechanical complication. Pushers, sub-dials, more dial-side real estate, more failure modes.
• NOT tourbillon. That's machinist territory and out of scope.
• NOT in-house grand complication (perpetual calendar, minute repeater, etc.). Out of scope.

Skills to demonstrate (acceptance criteria for "Watch 5 done")

• A complication that works correctly through a full operating cycle (chronograph: start/stop/reset; GMT: home and second timezone independently)
• Movement-specific maintenance done correctly (chronograph oils on chronograph movement; GMT bezel-click action smooth)
• Dial cutouts and sub-dial positioning aligned to the specific movement
• 21-day wear test (longer than other builds — complications need a longer characterization period)

Sourcing strategy — early thinking

If GMT path

• Movement: Seiko NH34 — widely available from Esslinger, Cousins UK, NamokiMODS. NH3x family — bench experience from Watches 1–3 carries over directly.
• Case: GMT-specific cases have an extra crown stem position and a bezel that rotates. Tandorio's GMT case selection is the starting point. Verify the bezel insert seating mechanism (bayonet, click, friction) and that Rob has the seating dies if a press is needed.
• Bezel insert: the GMT's second timezone. 24-hour scale, often two-tone (blue/red Pepsi, blue/black Batman, etc.). Typically aluminum or ceramic. Ceramic is harder; aluminum is more period-correct.
• Dial: GMT-compatible dial — typically has the GMT hand sweep cleared on the dial face. Standard 28.5mm fit on NH3x cases.
• Hands: four hands (hour, minute, second, GMT). The GMT hand has a distinctive arrow / triangular tip; sourcing must match the movement variant.

If chronograph path

• Movement: Seagull ST19 (budget, $80–150), Valjoux 7750 (mid, $400–800), Sellita SW500 (premium, $800+). The ST19 is a column-wheel chronograph; the 7750 is a cam-actuated chronograph (different mechanical feel at the pusher).
• Case: chronograph cases have two pushers flanking the crown. Pusher action and feel are sourcing decisions — soft pushers feel cheap; sharp pushers feel right.
• Dial: chronograph dials have 2 or 3 sub-dials (running seconds, minute totalizer, hour totalizer for some variants). Sub-dial position must match the movement layout exactly.
• Hands: more hands than any previous build (running seconds, chronograph seconds, minute totalizer, hour totalizer). Hand-setting time is multiplied.
• Crystal: typically domed sapphire; AR coating matters more on a chronograph (more dial information to read).
• Pushers: screw-down pushers on dive-style chronographs add water resistance but slow operation.

Risk register

• Chronograph oils touched: chronograph wheel-train re-oiling requires specific oils (Moebius 9415 for the chronograph friction surfaces, 9020 for jewels). Wrong oil = wrong viscosity = pusher feels off. Mitigation: don't touch the chronograph oils unless the pre-purchase service paperwork says they were freshly serviced.
• Sub-dial misalignment: sub-dial hands installed at the wrong zero point. Visible immediately. Mitigation: align to dial markings, not to assumed positions.
• GMT bezel insert mis-seats: the GMT hand reads correctly but the bezel insert position is off — the second timezone reads wrong. Mitigation: dry-fit the insert, verify orientation marker (typically a triangle at 12), then press.
• Pusher leak: chronograph pushers are gasketed; gaskets fail. Mitigation: replace gaskets at every service; pressure-test before declaring done.

Open questions

• GMT vs chronograph (this is the build's primary decision)
• If chronograph: ST19 budget / Valjoux 7750 mid / Sellita premium
• If GMT: Pepsi / Batman / black / other bezel insert color story
• Sport-leaning case (steel bracelet) or dressy-tool (leather strap)?

Open items

• Pick GMT vs chronograph
• Pick movement tier (if chrono)
• Pick bezel insert (if GMT)
• Decide bracelet vs strap

Watch 5 — Parts List

Source of truth for order status. Update rows in place — do not append duplicates.

Status values: proposed → ordered → shipped → received → installed

Spares / consumables

(empty until parts list firms up; chronograph build will need chronograph-specific oils — Moebius 9010, 9020, 9415)

Watch 5 — Build Log

Append-only chronological journal. New entries go at the bottom under a dated header.

Format: ## YYYY-MM-DD — short title

(empty until Watch 4 ships and Watch 5 sourcing begins)

Watch 5 — Notes

Free-form observations, mistakes, things to remember for future builds. Items here that generalize beyond watch_005 should be promoted to sourcing/compatibility_notes.md or sourcing/parts_database.md.

Pre-build observations (2026-05-10)

• The GMT path is the conservative choice — it's an NH34, the bench is already calibrated for NH3x family, and the only new skill is bezel insert seating. The chronograph path is the harder, more technically interesting choice but compounds risk significantly.
• For a first chronograph: start with the Seagull ST19. It's the cheapest of the three options, it's a column-wheel design (more interesting feel than cam-actuated 7750), and the lower stakes mean a botched build is recoverable. After ST19 success, a future Build 6 could revisit chronographs with a 7750 or SW500 at higher cost.
• 21-day wear test instead of 14: complications take longer to characterize. A chronograph's running-seconds rate is independent of the chrono-seconds rate; both need to be checked.
• No tourbillon. That isn't a five-watch project; it's a separate craft.